He's already stated he wants to get as much RAM as possible in there. Even if it's "only" a little more (300 MB is actually quite something, especially when it's the difference between something fitting in memory, and not), it fits the bill. And there'll be a performance improvement due to increased memory bandwidth with dual channel enabled, especially helpful in memory-stringent tasks.
Go for it. It's only another $15, as mentioned, so big deal. There was a time when 1 GB of memory would have cost you about $10,000.